The present invention relates to data networking, telecommunication networking, and, in one embodiment, to systems and methods for efficiently aggregating multiple Fibre Channel links.
The Fibre Channel standard defines a bi-directional link protocol, used to connect computers to disk drives and other peripherals. A typical Fibre Channel link may have a bandwidth of 1063 Mbps and a span of up to 10 kilometers.
One typical application of Fibre Channel is interconnecting computer CPUs with arrays of disk drive in large scale computing centers, as would be used in, e.g., financial transaction processing. For reasons of fault tolerance, it is desirable to locate redundant storage resources at remote locations. The advent of high data rate metropolitan optical networks including such networks based on the use of dense wave division multiplexing (DWDM) and/or SONET/SDH transport systems makes it possible to extend so-called storage area networks (SANs) that carry multiple Fibre Channel links over distances much longer than 10 kilometers.
It is useful to apply the widely prevalent Fibre Channel standard to communicate across DWDM networks and therefore minimize the need to redesign computing center equipment. Such DWDM networks can themselves employ protocol such as Gigabit Ethernet, 10 Gigabit Ethernet, SONET, etc. A single wavelength may thus carry e.g., a 1 Gbps data stream, 10 Gbps data stream, etc. Fibre Channel frames may be encapsulated within Gigabit Ethernet frames and/or SONET frames.
However, severe data transport inefficiencies may arise if Fibre Channel links are assigned to, e.g., Gigabit Ethernet links, 10 Gigabit Ethernet links, or STS-48 SONET envelopes based on maximum Fibre Channel throughput. Typically, the momentary aggregate bandwidth of the Fibre Channel links will fall far short of the total of the maximum bandwidths. Therefore, a straightforward mapping of transport network capacities to maximum Fibre Channel demands will result in unused capacity. It would be desirable to use capacity more efficiently and therefore reduce costs by allowing oversubscription to available transport capacity.
One approach to providing Fibre Channel oversubscription is described in U.S. patent application Ser. No. 10/366,867. The approach described therein typically employs an ingress buffer between a set of local Fibre Channel ports and a transport network. The ingress buffer should be as large as the sum of the flow control credit numbers negotiated between the local and remote ports. For certain Fibre Channel port implementations, this credit number may be very large and thus a very large ingress memory is needed. Since this memory should also be high speed, size will come at relatively high cost.
Flow control in this approach is handled by throttling the Fibre Channel ready indications received from the remote ports before forwarding them to the local ports. Since the remote Fibre Channel ports may be quite distant, there may be relatively large latency in communicating the ready indications. The latency involved in operating the flow control mechanism may lead to reduction of throughput.
What is needed are systems and methods for Fibre Channel oversubscription that allow for large flow control credit grants without requiring large ingress memories and that do not introduce excessive latency into flow control operations.